Learn English – gender-neutral prefix for “parent”

The prefix extro- means ‘outwards’. The Oxford English Dictionary has entries for both extrovert and extravert, with no difference in meaning. The only other word in the OED beginning with extro- is ‘extrospective’. Its Latin origin is the preposition extra which means ‘outside’. The ‘o’ appears to have replaced the ‘a’ of ‘extra’ by analogy with the Latin adverb intro.

Intro itself means ‘inwards’, ‘to the inside’, and is used in that sense as a prefix in English verbs and adjectives. Intra is a Latin preposition meaning ‘inside’ and is the origin of the prefix in English adjectives, typically those found in biological contexts.

Usually you can just slap re on the front of a word, without a hyphen, and you will be understood. There’s no need for the term to have made its way into an “authoritative” dictionary, even if there were such a thing.

There are circumstances in which the hyphen is desirable:

• if your new word with re collides with an established “re” word which has a different sense. Two of the words Carlo_R mentions are of this sort: resign and reserve.
• If you want to draw attention to the fact that you are using a “re” word in a different sense than that which would be expected, particularly if you are reverting to the base sense. “D.W.Griffith’s re-construction of the myth of the carpetbagger.”
• If you want to emphasize that you are repeating or reversing an action. “Burns opened an interesting question in 1923; but it has been completely neglected and I want to re-open it now.”

I sometimes intrude a hyphen when the word to which I’m attaching re begins with a vowel, to prevent even momentary confusion; but it’s probably not necessary.